Merge branch '4.1'

* 4.1:
  [appveyor] fix bis
  [appveyor] minor CI fix

Author: nicolas-grekas

.github/build-packages.php

@@ -14,7 +14,7 @@
 $flags = \PHP_VERSION_ID >= 50400 ? JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE : 0;
 
 foreach ($dirs as $k => $dir) {
-    if (!system("git diff --name-only $mergeBase -- $dir", $exitStatus)) {
+    if (!system("git diff --name-only \"$mergeBase\" -- $dir", $exitStatus)) {
         if ($exitStatus) {
             exit($exitStatus);
         }

appveyor.yml

@@ -45,7 +45,7 @@ install:
     - php composer.phar self-update
     - copy /Y .composer\* %APPDATA%\Composer\
     - php composer.phar global require --no-progress --no-scripts --no-plugins symfony/flex dev-master
-    - php .github/build-packages.php "HEAD^" src\Symfony\Bridge\PhpUnit
+    - php .github/build-packages.php %APPVEYOR_REPO_COMMIT%^^ src\Symfony\Bridge\PhpUnit
     - IF %APPVEYOR_REPO_BRANCH%==master (SET COMPOSER_ROOT_VERSION=dev-master) ELSE (SET COMPOSER_ROOT_VERSION=%APPVEYOR_REPO_BRANCH%.x-dev)
     - php composer.phar update --no-progress --no-suggest --ansi
     - php phpunit install